/*
 * Copyright 2009 Tran Nhut Trung.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and 
 * limitations under the License.
 */
package org.eclipse.core.databinding.observable.gwt.internal;

import com.google.gwt.event.logical.shared.HasValueChangeHandlers;
import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.ui.HasValue;
import com.google.gwt.user.client.ui.Widget;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.gwt.IWidgetObservable;


public class HasValueObservableValue extends WidgetPropertyObservableValue implements IWidgetObservable {
  private HasValue valueWidget;
  private Class valueType;

  private ValueChangeHandler valueChangeHandler = new ValueChangeHandler(){
    public void onValueChange(ValueChangeEvent event) {
      processUpdate(event.getValue());
    }
  };
  private HandlerRegistration valueChangeHandlerRegistration;

  public HasValueObservableValue(HasValue valueWidget, Class valueType) {
    this(Realm.getDefault(), valueWidget, valueType);
  }
  public HasValueObservableValue(Realm realm, HasValue valueWidget, Class valueType) {
    super(realm, (Widget)valueWidget, "value");
    this.valueWidget = valueWidget;
    this.valueType = valueType;
    
    this.oldValue = doGetValue();

    if (valueWidget instanceof HasValueChangeHandlers){
      valueChangeHandlerRegistration = (valueWidget).addValueChangeHandler(valueChangeHandler);
    }
  }

  public synchronized void dispose() {
    super.dispose();
    valueChangeHandlerRegistration.removeHandler();
  }

  protected void doSetApprovedValue(Object value) {
    try {
      updating = true;
      // valueWidget.setValue(value==null? "" : (String)value);
      valueWidget.setValue(value);
      oldValue = doGetValue();
    } finally {
      updating = false;
    }
  }

  public Object doGetValue() {
    if (valueWidget == null){
      return null;
    }
    
    return valueWidget.getValue();
  }

  public Object getValueType() {
    return valueType;
  }

  protected void processUpdate(Object newValue){
    if (valueWidget == null){
      return;
    }
    
    if (!updating) {
      if (!newValue.equals(oldValue)){
        fireValueChange(Diffs.createValueDiff(oldValue, newValue));
        oldValue = newValue;
      }
    }
  }
}
